Synthesis of Trisubstituted Alkenes via Direct Oxidative Arene–Alkene Coupling

The
use of an inorganic oxidant with an acetic acid/acetonitrile
solvent combination has been identified as optimal for direct arene/1,2-disubstituted
alkene oxidative couplings, providing an efficient route to trisubstituted
alkenes. The acetonitrile cosolvent dramatically accelerates the rate
of reaction, and an insoluble inorganic oxidant limits unwanted oxidation
of substrates. The scope of this procedure is illustrated with arenes
and alkenes containing electron-donating and -withdrawing substituents
resulting in a general synthetic strategy to trisubstituted alkenes.
In situ ESI-MS analysis of the reaction components has identified
the key Pd intermediates in the Fujiwara–Moritani catalytic
cycle.